The present invention relates to a method for producing a molded unit having a plurality of electrodes embedded therein.
An example of a known molded unit with electrodes embedded therein, which forms a rotational angle sensor for sensing the crank angle or position of an internal combustion engine, is shown in FIGS. 4 through 6 which are a plan view, a bottom view and a cross section along line VI--VI of FIG. 5, respectively. The molded unit includes a plurality of first through fifth electrodes 1, 2, 3, 4 and 5, as illustrated in FIG. 7, which are embedded in a circular-shaped molded body 6 formed of a resin. The molded body 6 has a plurality of through-holes 7 formed therethrough at the backside thereof which is opposite to that surface of the molded body 6 at which a plurality of recesses are formed for mounting electric elements 8.
The above-described molded unit is produced as follows. First, a plurality of electrodes 1-5, which are electrically and mechanically disconnected from each other, are respectively or individually placed in a mold at predetermined locations therein and exactly positioned or supported in place by a plurality of support pins. Then, a molten resin is poured into the mold and cooled to provide a molded body 6 having the electrodes 1-5 embedded therein. After cooling of the molten resin, the support pins are removed from the molded body 6, forming a plurality of through-holes 7 at the backside thereof, as shown in FIGS. 5 and 6. In this state, it is undesirable for one side of the surfaces of the electrodes 1 through 5 to be exposed to the outside of the molded body 6 through the through-holes 7. Therefore, the through-holes 7 thus formed are then closed by filling therein a sealing material such as a silicone-based adhesive. Such a filling operation is troublesome, adding to the cost of manufacture. In addition, it is rather difficult, cumbersome and inefficient to exactly and individually position the mutually separated electrodes 1-5 at their respective predetermined locations inside the mold.